Mechanical linkage

Abstract

A linkage ( 100, 200 ) having a plurality of small angle links ( 114, 116; 208, 212 ) with axes of rotation directed to a single point to allow movement of an recipient object without moving the point of action of an applied force (F).

What is claimed is: 
     
       1. A rehabilitation apparatus comprising:
 a force provider; 
 a recipient object, wherein the recipient object is a body part support; and 
 a linkage configured to transfer a force from the force provider to the recipient object, the linkage comprising a first link and a second link; 
 the first link having a first rotational joint defining a first link axis, and a second rotational joint defining a second link axis, the first and second link axes being at a first link angle to each other, which first link is pivotably attached to the recipient object for rotation about the first axis; and, 
 the second link having a third rotational joint defining a third link axis, and a fourth rotational joint defining a fourth link axis, the third and fourth link axes being at a second link angle to each other, the second link being pivotably attached to the first link such that the second and third link axes coincide, the second link being pivotably mounted at the fourth link axis to transfer a force from the force provider, 
 in which the first, second, third and fourth axes intersect at a predetermined point such that the recipient object can rotate about the predetermined point by articulation of the linkage; 
 in which the first and second link angles are each less than 45 degrees; and 
 in which the body part support is a foot support, and the force provider is configured to exert the force in a fore-aft direction of a subject's foot in use. 
 
     
     
       2. A rehabilitation apparatus according to  claim 1 , in which the body part support is configured to receive a body part proximate a joint so as to align an axis of rotation of the joint with the predetermined point of the linkage. 
     
     
       3. A rehabilitation apparatus according to  claim 2 , in which the body part support is configured to receive the body part proximate the joint so as to align a centre of rotation of the joint with the predetermined point of the linkage. 
     
     
       4. A rehabilitation apparatus according to  claim 2 , in which the push-pull rod and the actuator are configured to exert a force through the predetermined point. 
     
     
       5. A rehabilitation apparatus according to  claim 1 , in which the force provider is configured to exert a force in a first direction, and in which the first link axis is oriented at 80 to 100 degrees to the exerted force. 
     
     
       6. A rehabilitation apparatus according to  claim 1 , in which the first link is connected to the body part support at a lateral side of the subject's foot in use. 
     
     
       7. A rehabilitation apparatus according to  claim 1 , in which the force provider is a push-pull rod driven by an actuator. 
     
     
       8. A rehabilitation apparatus according to  claim 1 , in which each rotational joint is defined by respective bores in the links and a shaft extending through the respective bores. 
     
     
       9. A rehabilitation apparatus according to  claim 1 , in which each link comprises a body having a mid section, a first end section and a second opposite end section, the end sections being angled with respect to the mid section. 
     
     
       10. A rehabilitation apparatus according to  claim 9 , in which the rotational joints of the links are defined normal to respective end sections such that the sections are angled to provide the link angles. 
     
     
       11. A rehabilitation apparatus according to  claim 1 , in which the links are constructed from generally tubular bodies.